NameError: .box-shadow is undefined in /Users/haifeng/IT/01_Study/github_projects/js_framework/public/js/lib/bootstrap/3.0.0/css/popovers.less on line 20, column 3:
19   border-radius: @border-radius-large;
20   .box-shadow(0 5px 10px rgba(0,0,0,.2));
21 

